TV & SAT TV

Designing

We are very pleased to announce that SatNet 3.0 software has received the Award of the Ministry of Economy for the most innovative product or technology presented on the Elektrotechnika 2014 fair in Warsaw, Poland.

Implementation of a large SMATV system should be guided by the design taking into account information such as the levels of input signals, the signal levels at the outputs of active elements, attenuation of the cables and passive components of the system such as splitters, taps and subscriber outlets.

A movie showing the process of designing multiswitch system with the use of SatNet software from Terra.

Network planning and design with the use of a sheet of paper and a pencil is laborious and entails the risk of error. Free software from TERRA - SatNet 3.0 - allows to design installations based on the equipment manufactured by the company. The program allows to prepare the project in graphical form, to determine signal levels in all outlets and verify if they are compliant with standards, and to decide whether to use equalization function of the amplifiers. The program enables the user to archive the designs.

The family of TERRA devices allows to build very large SMATV systems (even up to 1000 outlets), with different options, both with centralized and decentralized power supply.

Before designing a system, one should know its components. At the beginning, we present a brief summary of the rich offer of TERRA multiswitches and auxiliary equipment.

Cascade network architecture allows for simple connection of further multiswitches using outputs of the last-level multiswitch and the inputs of the next-level one. The division into subnetworks (usually for distributing signals in staircases) is obtained by using splitters or taps. Example cascade network is shown in Fig. 8. The hardware implementation of the network is based on cascadable multiswitches of MS series. They are powered from an amplifier or power supply (18 VDC output) connected to the last multiswitch in the cascade. This type of multiswitches has passive terrestrial TV path and does not allow to adjust the gain of SAT path.

The multiswitches are designed for the simplest networks, mainly up to 32 outlets. Such installations based on single MSR multiswitches usually do not need special designs, unless they include long transmission cables. The multiswitches are also suitable for designing radial networks which consist of more than one device. In such installations the main paths distribute signals to the radial multiswitches through taps.

The multiswitches have active terrestrial path and provide the possibility of adjusting gain of the path, and - in the case of 9-input multiswitches - of one SAT path (position).

The flagship product of the TERRA company. Great opportunities in terms of network scalability. Installation of several hundred outlets may require only one power supply. The main idea of the network is the construction of signal bus which delivers the signals to each subnetwork with MV/MSV multiswitches (example - Fig. 10).

The multiswitches have active terrestrial path and provide the possibility of adjusting gain of the path, as well as of one or two SAT paths (independently Lo and Hi bands).

The multiswitches of MR/MSR and MV/MSV series provide built-in cable equalization function (compensation of higher loss for higher frequencies) and grouping the outputs according to signal levels (for different distances to the outlets).

The amplifiers allow for separate adjustment of all satellite lines (gain up to 22dB) and terrestrial TV path (gain up to 17 dB). Additionally, each amplifier is equipped with "slope" knob (or discrete swtiches for net5 series) enabling compensation of the attenuation of the cable. Maximum output level the amplifiers is 114dBuV (IMD3).

Due to the innovative concepts of Terra company (e.g. centralized power supplying from an amplifier), the important parameter of the amplifiers is the maximum current capacity. The amplifiers of SA series are capable of providing via the H lines up to 2 A (one multiswitch of MV/MSV series requires about 90 mA).

at the same address there is available presentation of the program capabilities (tutorial.exe),

there are planned next versions with increased functionality,

no need for installation,

required OS: Windows 98, XP, Vista,

minimum system requirements: 1GHz CPU, VGA 768x1024.

Capabilities

The application allows to design SMATV systems with the calculation of projected levels of terrestrial and satellite signals for each outlet in the network. This allows the designer/installer, sitting in front of the monitor, to predict what devices will be needed for distributing the signals and what settings like gain and cable equalization level (slope) will provide the desired results. In 99% of cases these settings fully correspond with the optimum values in real networks.

With a channel amplifier in the project, the frequency response for terrestrial path is limited to the bandwidth from the lowest to the highest channel selected. The graph is continuous, but the utility checks signal levels only for the selected channels.

Review of available configuration options

Notice: The 3.0 version of the application allows user to design "mixed" systems with the older and new versions of Terra equipment, which is especially useful in the case of expansion of existing systems. Because the devices can have different layouts of inputs, the software takes into account the possibility of using two types of multiswitch bus, with different order of cables. The order can be changed by pressing the Shift key once. The order of cables coming from LNB can be selected by choosing appropriate option of the input signals (see below).

Selecting the bus type at the input of the system

Example of connection of an "old" device (multiswitch) and the new one (amplifier)

defining acceptable signal levels in subscriber outlets/sockets

specifying transmission cables with attenuation (in dB/m, at 1 GHz)

Fig. 3. "Project Options" tab

Choosing "Project Options" tab, the user can define acceptable signal levels in subscriber outlets/sockets. As a rule, these values should be set between 50 to 75 dBuV for SAT TV and between 60 to 85 dBuV for terrestrial TV.

The values of outlet/socket loss can be found in catalog card of the product. The default values generally do not deviate significantly from reality.

SatNet program allows to select the kind of cable for the distribution network. The default options include 4 types: RG-59, RG-6, RG-7, RG-11. Clicking "Custom" field, the user can enter name and attenuation of any other cable, e.g. TRISET-113. Its attenuation at 1GHz can be found in the catalog card. It can be also read from the table below (as well as for another cable - RG-6). Attenuation values for other frequencies are calculated based on an algorithm developed by the software developers. During the simulation, one can see that the attenuation grows with frequency, which agrees with the real parameters of the cables.

The evaluation allows to assess satellite signal levels in the location of the system and is very useful when they cannot be measured physically. It is launched by selecting Run -> Path Loss Calculator.

Fig. 4. Path Loss Calculator

The user should define the position of the satellite (Hotbird 13° E, Astra 19.2° E), the level of EIRP (coverage maps can be found on the websites of the operators - Eutelsat and SES Astra), the coordinates of the receiving point, antenna gain (or its diameter and efficiency), and the LNB gain. After entering all the data and clicking "Calculate Signal Power", the calculator will show the estimated signal level in the reception point.

After placing the LNB on the application desktop and double-clicking on it, the user can enter the levels measured on the input of the distribution network. Since multiswitch systems employ quatro LNBs, the values can be given for every band-polarization pair. The data will increase the accuracy of the simulation. However, the simplest solution is is to tick the box "Use average values", determining one level for all transponders within one pair of polarization-band (the level that has been estimated with the use of the built-in calculator - see the step above).

The window also includes LNB current box for entering the rated value. All the data can be saved for future reference.

terrestrial TV signals

Fig. 6. Terrestrial channel levels (Channel power map)

Similarly to the satellite signals, the user can input the power levels of the terrestrial TV signals. In this case, the number of transponders means the number of received channels. While in the case of satellite signals it is not so important to enter measured values, the power levels of terrestrial channels should be definitely measured as they may differ very much due to many reasons.

Installation description: cascade network with 16 outlets, based on 3 cascadable multiswitches MS-553 and one end-of-line multiswitch - MS-554. Distribution of satellite signals from one satellite, in one staircase (four floors, each with four outlets).

After designing the network and running the simulation, the colors of the outlets say whether the levels of the output signals are within the limits specified by the user. If everything is OK, the outlets are are marked in green; red means excessive signal (risk of overdriving the receiving equipment), blue - too low signal (inadequate S/N ratio).

The Fig. 8. shows the simulation results. In all outlets the satellite signals fall within acceptable limits. Clicking on the output socket allows detailed examination of signal level across the whole frequency range.

TERRA multiswitches of MS series have passive terrestrial path. The tap attenuation in terrestrial TV band is 18 dB. Therefore, the network described above provides too low levels of terrestrial signals in the terminal sockets. Clicking on the blue spot, the user gets information on the deficiency details, including frequency characteristics. The fig. 9. shows the frequency response of the terrestrial path for one of the sockets.

The figure shows that the level of the received signal is about 45 dB - lower than the assumed minimum level by 15 dB (blue line).

There are two solutions to that problem. The first one is use of SA-501/SA-51 or SA-511/SA-51D amplifier. However, this solution is not optimal, because the levels of the amplified satellite signals can be too high in the upper part of the installation. More appropriate results are provided by the use of a separate building amplifier for terrestrial path at the input of the distributing network. An example of such an amplifier is TERRA HA-126 R82303.Because the SatNet program does not include the use of such devices, this problem should be solved in an indirect way - by defining the level of the signal at the input of the terrestrial path at appropriate level, e.g. 102 dBuV. It will resolve the problem of too low terrestrial TV signals in the example network.

Case 2

Installation description: network with 72 outlets, distribution of signals from 2 satellites, division into 3 subnetworks (3 staircases) through taps with different tap attenuation. MSV multiswitches allow to power the whole system with SA-901 amplifier.

Fig. 10. Network with 72 outlets based on MSV-924 multiswitches

The design makes use of the possibility of adjusting gain of satellite paths of the MSV-924 multiswitches.

Important issue which must be borne in mind when designing networks with long runs of cables is the cable characteristics equalization available in SA amplifiers. The Fig.11. presents the situation in the furthest outlet in the second staircase, both without and with equalization function (-6 dB setting with the Slope knob of the SA-901 amplifier).

Fig. 11. Frequency response in the outlet without (on the left) and with equalization function (on the right) of the SA-901 amplifier

This feature allows to level the interesting channels in the outlet. According to current standards, the maximum difference in levels across the whole frequency range is 12 dB. In the first case, the difference is about 10 dB, while the use of the cable characteristics equalization function allows to reduce it to about 5 dB.

Below there is a part of the design performed with the SatNet2.0 program. The whole network has been divided with SS-904 splitter into 2 large subnetworks. All the devices in the subnetworks are powered through H lines from SA-901 amplifier. Each staircase has been equipped with tap and MSV-916 multiswitch. The taps used have different tap attenuation due to the need for compensation of signal level differences in individual staircases. Because of long cable runs, the SA-901 amplifiers use the equalization function (Slope).

Fig. 13. A part of the design with 120 outlets

The SatNet2.2 program allows to design SMATV systems practically without any restrictions. Experience says that the settings suggested by the application are optimal in 99% of real situations. DIPOL sincerely encourages designers and installers to use this program for their tasks.